Why is fall “Fall” in the northern hemisphere and “Spring” in the southern hemisphere?
The “axis” of the Earth is an imaginary line that passes from the north pole through to the south pole. If one looks at the orbit (path) of the Earth around the sun, the axis of the Earth is slightly tilted. What that means is that, for almost all of the year, EITHER the north pole OR the south pole will be tipped a little bit more toward the sun than the other pole. When the north pole is tipped slightly closer to the sun, then the northern hemisphere has summer! When it is tipped slightly away from the sun, then the northern hemisphere has winter! It is hard to imagine that what we see as a “small tilt” can really affect our weather, but that tilt has a huge impact on the amount of energy in our sunlight.
Check out this video made by MIT students that gives a great explanation for the seasons: